Axial flow compressor construction



Aug. 13,, 1953 5 STALKER 2,649,243

AXIAL FLOW COMPRESSOR CONSTRUCTION I Filed Aug. 5,, 1948 2 Sheets-$ 189 IN VEN TOR.

3953 E. A. STALKER AXIAL 110w COMPRESSOR CONSTRUCTION 2 Sheets-Sheet 2 Filed Aug. 5, 1948 AIR ENTERING ROTOR JNVENTOR.

Patented Aug. 18, 1953 UNITED STATEti mam OFFICE My invention relates to compressors and parc lla y to axial flow compressor construction.

An object of the invention is to provide a type of structure which is cheap to fabricate.

Other objects will appear from the description, drawings and claims.

I accomplish the above objects by the means illustrated in the accompanying drawings in which- Fig. 1 is an axial section through a radial difiusion compressor of five stages; I

Fig. 2 is a fragmentary development of the first rotor and stator of the compressor;

Fig. 3 shows the velocity vectors and a frag mentary development of the rotor;

Fig. 4 is an exploded view to show a method of fabrication;

Fig. 5 is a radial view of a stator blade and a fragment of the inner ring;

Fig. 6 is a view along line 66 of the blade only of Fig. 5;

Fig. '7 is a fragmentary radial view of a rotor stage of streamline or hollow blades and their blade plates;

Fig. 8 is a fragmentary perspective view of a rotor blade and ring of Fig. 7

Fig. 9 is a radial view of a blade part along line 9-5) in Fig. 10, forming the lower surface of a blade, shown on a fragment of the blade plate;

Fig. 10 is a side view of the blade part of Fig. 9;

Fig. 11 is a fragmentary section of the rotor of Fig. 8 taken transverse to the axis of rotation;

Fig. 12 is a radial view of fragments of blade plates contributing parts to a blade having an induction slot; and

Fig. 13 is a radial view of fragments of blade plates contributing parts to a blade having an eduction slot.

Axial fiow compressors require a great many blades. For instance a current eleven stage compressor has 22 00 blades. Since each of these blades has airfoil Sections of different shape at all chordwise sections along the length which must be machined accurately, their cost is very high. The hub and case must also be machined accurately to receive the blades. The blades are handled individually with the accumulation of large costs.

The present invention provides a construction for the rotors and stators, which does not require individual fabrication and installation of the blades. This type of construction achieves ity V2 is less than the inlet velocity V1. absolute velocity of the air leaving rotor 22 is scribed in my Patent No. 2,344,835 entitled Pumps issued March 21, 1944.

Briefly a radial diffusion compressor is one which expands the fluid radially as it flows between the blades with a general movement in the direction of the axis of rotation.

Fig. 1 shows an axial section through a radial diffusion compressor having five stages. Fig. 2 shows a development of the first rotor and stator. Fig. 3 shows the vector diagram for the rotor.

The axial velocity of the fluid rotor 22 is C1,

the relative peripheral velocity is U, and the resultant relative velocity is V1. Due to the radial expansion of the flow in the rotor, the exit veloc- The C2. The flow has had the whirl velocity AC added to it, which accounts for the pressure rise of the stage.

It will be observed from Fig. 2 that the leading edge of one blade overlaps the trailing edge of the next blade when viewed along the axis of rotation. This overlapping precludes integral stamping or forging the rotor and its blades. Fig. 4 shows how it is possible to fabricate the unit from stampings.

Each blade plate 20 has a plurality of blades 22. A second blade plate 23 has blades 24 similar to blades 22.

The cylinder 25, sometimes called the hub or rim means, has a plurality of slots 26 out in its wall. These slots have the same pitch angle as the blades 22 and 24. The cylinder has an inside flange 2! at one end which is not slotted and serves to aid in holding the slotted wall together in the fabrication process.

The blades on each plate are spaced so that they go into alternate slots 26. With both plates in place all slots are filled with blades. The blades are fused at their roots to the cylinder wall by silver solder, brazing, welding or other suitable means. The blade plates and spacer plate 28 may all be fused together and fixed to hub ring 30 and to the rotor shaft 29.

It will be readily understood that each plate is insertable in cylinder 25 by a forward motion accompanied by a small rotational motion.

Although two plates are shown in the Fig. 4 more plates might be used with proper spacing of the blades thereon.

The stators are formed similarly to the rotors as shown in Figs. 1, 5 and 6. The stator blades are straight along their fore portion 32 and curved along their aft portion 33. The portion 35 in the slot is straight throughout so that it completely fills the slot. The exposed end of the portion in the slot is flush with the surface of the ring. The trailing edge of the blade is marked T. E. to aid in interpreting Figs. 5 and 6.

Fig. 1 shows that the stator blade 32 for instance has its outer end fixed to the ring 36. The blade may be inserted in a slot in this rin or be simply fused to it.

The radial difiusion compressor is efiicient with plate type-blades which are simply rounded at the leading edge and sharpened at the trailing edge.

If it is desired to make the efficiency retain a high value over a wider range of fluid flow per revolution the blades may be given a streamline form. This type of construction is suitable for the rotors of conventional axial flow compressors which are peripheral diffusion machines.

In the streamline blade form, each blade plate carries only a part of a blade. Thus in Figs. 7 to 11 the two plates 40 and ii carry respectively the upper and lower portions of the blade 44. These two blade supporting plates have their complementing parts 42 and 43 in contact to form the blade 44. These plates provide part of the rotor blades and other blades 50 are supplied by similar plate sets 45 and 46 having respectively the blade parts 48 and 49. The blades formed by the respective plates are interspaced about the periphery of the rotor. This procedure permits the blade parts to be spaced on the respective plates sufiiciently to form the parts integral with the central portion of the plate.

The blade parts are scarfed at the trailing edges so that when they are fused together they form a sharp trailing edge for the blade.

The blade parts are joined at the nose by joggling the lower part and fusing the joint preferably by brazing or soldering. Any crevice at the joint may be filled with the solder so the surface will be smooth.

The blade parts at their tip ends have relatively short flanges 5| formed integral therewith.

These flanges preferably are about the extent of the fillet radius at their junction with the main surface of the blade part. The fillets have a preferred radius of th order of 5% of the chord length of the blade near the blade tip.

The blade plates such as 4| and 46 are fixed to the hub 52, fixed in turn to the rotor shaft 53. The fixing is preferably accomplished by welding.

The rotor plates 54 and 55 are flanged and the inner shroud elements 56 are welded or fused to the flanges. These elements fit snugly to the contour of the blades but are not necessarily fixed to them. The out-turned flanges of the rotor plates facilitate the welding by automatic machine methods.

When a blade with slot 12 is desired three plates may be used to make up the three blade p'arts 6i!62 as shown in Fig. 12. These parts are respectively parts of plates 6355. It would also be practical to use only two plates and weld the part 52 as an independent piece to the part 6| in spaced relation to part to form the slot 12.-

The slot may also be an over-lapping type of slot 14 as shown in Fig. 13. Here the part corresponding to 62 is 69 and the forepart Hi corresponds to 60, of Fig. 12.

In this invention the rotors are compressor rotors for increasing the static pressure and density of an elastic fluid. In order to achieve a significant change in density with an axial flow compressor each rotor must be operated at a speed high enough to effect a significant change in density, that is a change which in magnitude is outside the usual order of engineering accuracy in the industry. Thus machines are considered to be compressors as distinguished from fans at tip speeds of about 400 feet per second or more. At such a speed the average change in density over the blade length is about 3% which is just about or above the common order of accuracy of measurement of the density. Such compressors are expected also to operate at blade tip speeds close to the velocity of sound. At such speeds the change in pressure is maybe more than 70% or more than 10 pounds per square inch for air inducted at atmospheric pressure.

Since there is a substantial pressure rise from front to rear of a rotor the ratio of the hub radius to the blade tip radius is relatively large of a value of the order of 0.5 and preferably greater so that the pressure difference between front and rear sides can be sustained without a return flow at the hub such as occurs in a fan. For the same reason the blades are spaced peripherally close together, preferably about one chord length or less apart.

Commonly half to all the pressure rise occurs in the rotor between the leading and trailing edges. To sustain such an increase in pressure along the rotor passages from leading to trailing edges of the blades the hub rim between adjacent blades and from leading to trailing edges must be a fair and continuous surface. Also at all rotative speeds the case must fit closely about the blade tips which are contoured to the cylindrical surface of the case along substantially the whole length of the blade chord.

To dilTuse the flow between blades to achieve a pressure rise the flow must follow the blade surfaces without eddies. Accordingly the blades must have rounded leading edges. They must have sharpened trailing edges to be efficient.

Because of the high rotative speeds and the substantial increases in pressure and density of the fluid, positive means of driving the compressor rotor is provided. The shaft 29 is fixed to the hub rings 30 which in turn are fused to the disk 28 and also to the side plate 2?. The side plates are fused to the blades at their root ends. Thus the shaft can transmit the relatively high torque required to the disk and side plate and through each to the rotor blades.

Great lightness of the structure is achieved by joining the blades directly to the central disk 28 by fused metal. The blades are each joined by the sheet metal neck or element 2| extending from the blade root to the disk. This element fays the side surface of the disk defining therewith a soldered joint which thus carries its load in shear.

By arranging the joint in this manner, heavy blade bases are eliminated and with them a rim wall which would be thick in the radial direction to accommodate the blade bases. Thus the rotor is relieved of the rim pieces between bases which load up the inner part or unslotted part of the rim without contributing any strength for carrying the peripheral stress in the disk.

Thus by making the blades of sheet metal they are of light weight. By eliminating blad bases and extending light sheet metal structure radially inward to the disk28 the rim is very light weight and the whole rotor is consequently very light and is strong with all these parts made of thin sheet metal of substantially the same order of thickness as the blade sheet metal.

Since the rotor is to operate at high speed the rim is supported by being fixed to each of the blades or to the root ends thereof, that is at peripherally spaced points, which also makes possible a very light rim wall.

' The types of construction described eliminate the individual fabrication of. the blades and therefore the necessity of fitting each :blade to a rotor or drum. Since the centrifugal force from the weight of the blades and their attachments are the chief load on the rotor a great saving in rotor weight is achieved. amount to about 40 per cent of the rotor weight.

Furthermore since stampings are so cheap to produce and since the individual fabrication and fitting of the blades are eliminated great savings in cost are effected. The present invention therefore has outstanding advantages of lightness and cost.

I use the term cylinder to refer to any hub structure having a surface disposed circuitously about the axis of rotation.

Cross reference is made to my copending application, Serial No. 38,904, filed July 15, 1948 covering similar subject matter.

While I have illustrated a specific form of this invention it is to be understood that I do not intend to limit myself to this exact form but intend to claim my invention broadly as indicated by the appended claims.

What is claimed is:

1. In combination in an axial flow elastic fluid compressor rotor of light weight for operation in an enclosing casing, a rotor disk of sheet metal, a plurality of peripherally spaced sheet metal blades having rounded leading edges and sharp trailing edges adapting said blades to operate at high tip speed to accelerate and diffuse efficiently fluid flowing between said blades in the general axial direction, each said blade having a sheet metal element extending radially inward to said disk and being fixed to a side surface thereof, a hub ring fixed to said disk at a locality substantially inward from the root ends of said blades, shaft means to apply torque to said hub ring to rotate said blades at a sufliciently high tip speed to increase substantially the pres sure and density of said fluid flowing between said leading and trailing edges, sheet metal rim means having a generally cylindrical wall extending peripherally between blades and from leading to trailing edges of said blades at the root ends thereof to sustain the increase in said fluid pressure and density between said blades, said blades being fixed to said rim wall, and said rim means being permanently fixed to said hub ring to cooperate with said disk in transmitting said torque to said blades.

2. The structure of claim 1 wherein said blades, rim means and rotor disk are all of thin sheet metal of substantially the same order of thickness.

3. In an elastic fluid compressor having an enclosing casing, a rotor assembly comprising a plurality of axially spaced rotors mounted in This may readily:

said casing for rotation about an axis, a plurality of stators interspaced with said rotors, said stators having a plurality of peripherally spaced blades, each said rotor comprising a rotor disk of sheet metal, a plurality of peripherally spaced sheet metal blades having rounded leading edges and sharp trailing edges adapting said blades to operate in said casing at high tip speed to accelerate and diffuse efficiently fluid flowing between said blades in the general axial direction, each said blade having a sheet metal element extending radially inward and fixed to said disk, a hub ring fixed to said disk at a locality substantially inward from the root ends of said blades, shaft means to apply torque to said hub ring to rotate said blades at asufficiently high tip speed to increase substantially the pressure and density of said fluid flowing between said leading and trailing edges, sheet metal rim means having a generally cylindrical wall extending peripherally between blades and from leading to trail? ing edges of said blades at the root ends there of to sustain the increase in said fluid pressure and density between said blades, said rim wall extending in the general axial direction with the forward and rearward edges thereof respectively at substantially the level of the inner ends of said stator blades at the opposite ends of said wall to direct fluid from one compressor stage to the other, said rim means being permanently fixed to said disk to cooperate therewith in transmitting said torque to said blades.

4. In an axial flow elastic fluid compressor rotor of light weight for operation in an enclosing casing, a rotor disk of sheet metal, a pair of sheet metal blade plates on opposite sides of said disk each having blades peripherally spaced thereon formed with rounded leading edges and sharp trailing edges adapting said blades to operate at high tip speeds in said casing to accelerate and diffuse efficiently fluid flowing between said blades in the general axial direction, each said blade plate having a sheet metal element extending radially inward to said disk and being fixed thereto on opposite sides thereof, sheet metal rim means extending peripherally in a generally axial direction between adjacent blades and continuously from leading to trailing edges of said blades and fixed thereto to sustain a static pressure increase in fluid flowing rearward between said blades, said rim means having a radially inwardly directed flange connected to said rotor disk, and a hub ring connected to said disk for transmitting torque to said blades.

5. In combination in an axial flow elastic fluid compressor rotor of light weight for operation in an enclosing casing, sheet metal blade means comprising a plurality of peripherally spaced sheet metal blades and a sheet metal structure extending radially inward from the roots of said blades and fixed thereto, said blades having rounded leading edges and sharp trailing edges adapting said blades for compressor operation in said casing at high speeds to accelerate and diffuse emciently fluid flowing between said blades in the generally axial direction, a sheet metal rim means extending in a generally axial direction between said blades at a locality thereon outwardly adjacent the root ends thereof and from leading to trailing edges of said blades to sus tain an increase in fluid pressure between said edges, each said blade being fixed to said rim means, a hub fixed to said sheet metal structure at a locality radially inwardly of said blade roots to rotate said blade means, and a side plate fixed to said rim means and to said hub for supporting the centrifugal load on said rim means.

6. An axial flow elastic fluid compressor rotor as defined in claim in which the blades are hollow.

7. In combination in an axial flow elastic fluid compressor rotor of light weight for operation in an enclosing casing, sheet metal rim means, a side plate fixed to said rim means, sheet metal blade means comprising a plurality of sheet metal blades peripherally spaced about said rim means and a sheet metal hub structure fixed to said blades and extending radially inward from said rim means to said side plate and being fixed directly thereto, said blades having rounded leading edges and sharp trailing edges adapting said blades for compressor operation at high tip speed to accelerate and difl'use efficiently fluid flowing between said blades in the general axial direction, said sheet metal rim means extending between said blades in a generally axial direction at a locality thereon outwardly adjacent the root ends thereof, each said blade being fixed to said rim means adjacent the root ends of said blades, said rim means extending between adjacent said blades and from the leading to the trailing edges thereof to sustain a substantial increase in static pressure in said fluid fiowing between said blades, and a hub element fixed to said side plate to rotate said blade means.

8. In an axial flow elastic fluid compressor of light weight, a sheet metal hub structure, means to sustain a substantial pressure difierence between the front and rear sides of said structure comprising a casing to house said hub structure for rotation about an axis, a plurality of sheet metal blades carried on said hub structure and adapted to retain a substantially constant tip diameter while being rotated and contoured at their tips to fit closely to said casing along substantially the entire chord thereof, said blades having rounded leading edges and sharpened trailing edges adapting said blades for operation at high tip speeds to accelerate and diffuse efficiently fluid flowing between said blades in the general axial direction, rim means fixed to said hub structure and extending peripherally between blades and in a generally axial direction between the leading and trailing edges of said blades at the root ends thereof to sustain an increase in fluid pressure between said edges, each said blade having a radial length not greater than the maximum radius of said rim means for cooperation in maintaining said pressure difference, and each said blade being fixed to said rim means.

9. An axial flow elastic fluid compressor rotor as defined in claim 8 in which the blades are hollow.

EDWARD A. STALKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,326,871 Junggren Dec. 30, 1919 1,827,316 Haynsworth Oct. 13, 1931 2,234,319 Preston Mar. 11, 1941 2,237,039 Newnham Apr. 1, 1941 2,294,586 Troller Sept. 1, 1942 2,397,171 Troller 1 Mar. 26, 1946 

